Artificial valve prosthesis with improved flow dynamics

ABSTRACT

An expandable venous valve having a support structure configured to enlarge the area adjacent the valve structure. The enlarged pocket areas can be created by forming an artificial sinus adjacent the valve structure in an unsupported section of vessel wall between two support frame sections.

TECHNICAL FIELD

This invention relates to medical devices, more particularly tointravascular valve prostheses and the like.

BACKGROUND OF THE INVENTION

The venous system includes a series of valves that function to assistthe flow of blood returning to the heart. These natural valves areparticularly important in the lower extremities to prevent blood frompooling in the lower legs and feet during situations, such as standingor sitting, when the weight of the column of blood in the vein can actto prevent positive blood flow toward the heart. This condition,commonly known as ‘chronic venous insufficiency’, is primarily found inindividuals in which gradual dilation of the veins, thrombotic events,or other conditions prevent the leaflets of the native valves fromclosing properly. This leads to significant leakage of retrograde flowsuch that the valve is considered ‘incompetent’. Chronic venousinsufficiency is a potentially serious condition in which the symptomscan progress from painful edema and unsightly spider or varicose veinsto skin ulcerations. Elevation of the feet and compression stocking canrelieve symptoms, but do not treat the underlying disease. Untreated,the disease can impact the ability of individuals to perform in theworkplace or maintain their normal lifestyle.

To treat venous valve insufficiency, a number of surgical procedureshave been employed to improve or replace the native valve, includingplacement of artificial valve prosthesis. These efforts have met withlimited success and have not been widely adopted as a method of treatingchronic venous insufficiency. More recently, the search has been to finda suitable self-expanding or radially-expandable artificial valve thatcan be placed using minimally invasive techniques rather than requiringopen surgery and its obvious disadvantages. Thus far, use of prostheticvenous valves has remained experimental only.

While attempts have been made to mimic the function of the naturalvalve, there is no expandable valve for venous transcatheter placementthat includes a combination of the native structural features thatindividually or collectively, may prove highly advantageous or criticalfor a successful valve. One common problem evident from earlyexperiences with prosthetic valves is the formation of thrombus aroundthe base of the leaflets, probably due at least in part to blood poolingin that region. In a natural valve, the leaflets are typically locatedwithin a sinus or enlargement in the vein. There is some evidence thatthe pockets formed between the leaflets and the walls of the sinuscreate vortices of flowing blood that help flush the pocket and preventblood from stagnating and causing thrombosis around the valve leaflets,which can interfere with the function of the valve. It is thought thatthe stagnating blood prevents oxygen from reaching the endotheliumcovering the valve cusps, leading to hypoxia of the tissues which mayexplain increased thrombus formation typical in that location.Expandable-frame valve prostheses typically are of a generallycylindrical in shape and lack an artificial sinus or pocket space thatis sufficient for simulating these natural blood flow patterns. What isneeded is an intravenously placed artificial valve that is configured tocreate more effective flow patterns around the valve structure tocirculate the blood or bodily fluids and reduce the likelihood ofstagnation and the potential clinical problems that may result.

SUMMARY OF THE INVENTION

The foregoing problems are solved and a technical advance is achieved inan illustrative valve prosthesis, such as an artificial venous valve,having a valve structure and a self-expanding or otherwise expandablesupport structure that upon deployment within the vein, helps create anartificial sinus or larger pocket in the vessel surrounding the valvestructure of sufficient size and shape to stimulate flow patterns orvortices which facilitate clearing of the blood or other bodily fluidthat would otherwise pool therein. The structural adaptations result inmore turbulent flow, increased velocity of flow, larger and/or morenumerous vortices, other factors, or a combination of the above thatprevent stagnant, hypoxic areas from occurring around the valvestructure. Furthermore, the modified flow may also contribute to helpingclose the leaflets to form a seal and prevent leakage of fluid backthrough the valve. The artificial sinus or enlarged pockets simulate thefunction of the natural sinus that exists at the site of most naturalvalves in the deep veins of the lower legs and which may explain why theproblem of thrombus forming around the valve structure has been observedto be a common problem in prosthetic venous valve designs lacking such asinus area.

In one aspect of the invention, the collapsible support structure of thevalve prosthesis is expandable to a particular diameter upon deployment,with the valve prosthesis being configured such that the prosthesisincludes an intermediate, substantially ‘open’ section such that theartificial sinus is created by a portion of the duct or vessel that issubstantially unsupported by the support structure. The unsupportedportion of the vessel can advantageously assume a diameter that islarger than the deployment diameter of the vessel-anchoring or ‘closed’sections or portions of the collapsible support structure, therebycreating an artificial sinus as blood (or bodily fluid) exerts pressureon the unsupported portion of the vessel wall. In one exemplaryembodiment, the expandable support structure comprises a first, proximalportion and a second, distal portion that are interconnected by one ormore thin members or struts, such that the largely unsupported regionbetween the first and second (proximal and distal) sections of thesupport structure forms an artificial sinus (proximal being definedherein as have the same positional orientation as the orifice or openingof the valve structure, which is typically toward the heart in a venousvalve). The valve structure is attached about the support structure suchthat it is largely situated within the unsupported region forming theartificial sinus. For example, the valve structure (defined herein asone or more cooperating leaflets, tubular members, or any flexiblestructure adapted to seal a passageway in response to changing fluidpressure differentials thereacross) may be attached to theinterconnecting members, which can comprise oppositely placed strutshaving attachment points, (e.g., suture or any suitable structure ormethod) to facilitate attachment of the valve material.

In another aspect of the invention, the expandable support structure ofthe valve prosthesis comprises a framework or anchoring portion havingan intermediate region that includes an enlarged diameter configured tocreate an artificial sinus about the valve structure, which is attachedinside the intermediate region. In one embodiment, the support structureis made of a superelastic material, such as nitinol, and theintermediate region comprises an expanded or bulging portion that isformed by heat setting the nitinol tubular frame around a mandril orother fixture of the desired configuration using a method well known inthe medical arts. The intermediate portion expands to a diameter largerthan the proximal and distal portions when the prosthesis is deployedfrom the delivery system, thereby producing larger pockets around thevalve structure which create more effective flow patterns to reducepooling. In another embodiment, the proximal, distal, and intermediatesections are separate, interconnected sections, such as zig-zag frame orother expandable or self-expanding support or anchoring frames. Theintermediate section comprising the artificial sinus includes a firstand a second radially expandable or self-expanding portions in which theadjoining ends of each are larger in diameter than the ends which adjointhe proximal and distal sections, respectively. The frustoconical shapeof the respective intermediate sections can be accomplished by eitherforming the section into that shape (i.e., plastic deformation of atubular prosthesis, heat setting nitinol, laser cutting a frustoconicalsection of tubing, etc.) or a constraining means, such as a suture orthin wire, can be used to manipulate the relative diameters by feedingthe constraining means through the apices of the bend or aperturestherein and applying the appropriate amount of tension to create thedesired shape. Optionally, a tubular or band-like section can bepositioned between opposing frustoconical sections to create a longerartificial sinus.

In yet another aspect of the invention, the proximal end of thecollapsible support at which the valve structure is located is expanded(e.g flared outward) such that the expanded end or a combination of theexpanded end and adjacent area of the vein forms the artificial sinus.

In still yet another aspect of the invention, the proximal and distalsections are configured to include a substantially open area betweenthem with the valve structure being attached to the distal section suchthat it is positioned just below the artificial sinus. Optionally, asleeve of a biomaterial (e.g a bioremodelable material such as smallintestinal submucosa (SIS) or another collagenous extracellular matrix)or fabric can be attached over the proximal and distal sections suchthat it forms a seal between the prosthesis and the vessel wall,including the artificial sinus.

In still yet another aspect of the present invention, the supportstructure of the prosthesis is configured such that the attachmentpathway (defined herein as the interface between the lateral, outeredges of the leaflets and the struts and/or vessel walls to which theyare attached to establish and define the shape and configuration of theplurality of leaflets comprising the valve structure as deployed) has afirst, proximal portion in which the one or more longitudinal attachmentstruts extending from the proximal bends or commissures that carry andsupport the proximal outer edges of the leaflets (and span the orifice)have a strongly longitudinal orientation with respect to thelongitudinal axis of the prosthesis and valve structure, and a distalportion of the attachment pathway that extends circumferentially(laterally) and distally from the longitudinal axis to form the bottomor distal edge of the outer leaflet edge or perimeter. When viewed fromthe side, the support frame and attached leaflet is configured such thatthe angle (angle .alpha.) formed between the opposing leaflets, ascarried along the proximal attachment pathway, is substantially lessthan the angle (angle .beta.) formed between distal attachment pathwaysand the vessel walls. This configuration results in leaflets havinglarge coaptable area relative to the overall surface area, whichimproves sealing (including reducing the effects of retraction by thevalve material) and allows for larger pockets surrounding the leafletswhich, like the sinus, facilitate the creation of larger, strongervortices of retrograde flow that help close the leaflets and clear awayblood or fluid that could otherwise stagnate under conditions where thesurrounding pockets are smaller in size. As used herein, the term‘retrograde flow’ is defined as bodily fluid traveling in a distaldirection (toward the feet), whether due to gravitational forces,redirection due to contact with the prosthesis or bodily lumen walls, orby some other means.

A first embodiment of this aspect of the invention includes a framecomprising a pair of longitudinal attachment struts originating fromeach commissure bend. The struts extend in generally longitudinaldirection, diverging relatively or not at all toward the distal end ofthe prosthesis before more acutely diverging as they curve laterally andcircumferentially away from the proximal strut portions such that thetransition between the proximal and distal portions of attachmentpathway comprises a bend having a radius that is distinctly smaller thanthat of the adjacent strut portions (the proximal portions beingstraight some embodiments). The distal attachment pathways converge todefine the bottom outer edge of each leaflet. In a second embodiment ofthis aspect of the invention, the support frame of the prosthesisincludes a pair of substantially parallel longitudinal attachment strutsto which the leaflets are attached to form the proximal portion of theattachment pathway, and distal attachment struts extendingcircumferentially and laterally outward from the substantially parallelstruts to form the distal portion of the attachment pathway. The supportframe carrying the valve structure may be advantageously comprised ofradial sections (e.g., quadrants in a bicuspid valve) that are of anidentical pattern but with alternating orientation such as to providefor radial stability and better expandability characteristics. Theradial section not carrying the leaflet proximal outer edges serves aslateral support structure for adding longitudinal stability and helpprotecting the leaflets from adhering to the vessel walls. The parallelstruts provide for advantageous bending and torsional characteristicssuch that the frame has utility as a stent. In an alternate embodimentof the support structure, the lateral outer edges of the opposingleaflets can be attached to single longitudinal attachment strut havinga pair of distal struts extending laterally outward andcircumferentially to carry the bottom half of the leaflet and define theoverall shape thereof. The strut may be thicker than adjacent struts andinclude aperture therealong for facilitating attachment of the valvestructure.

In still yet another aspect of the present invention, the proximalsection of the valve is wider in diameter at its proximal end, whichanchors the prosthesis in the vessel, and narrower at the interfacebetween the proximal and intermediate sections. This, in combinationwith a leaflet structure that maximizes pocket size, results inretrograde flow being subject to a Venturi effect which increases flowand the strength of the vortices to close the valve and clear thepockets of potentially stagnating fluids.

The configuration of the basic units of the support structure and valvestructure is not particularly critical for an understanding of theinvention. Numerous examples are well known in the prior art and may befound in the disclosure of Applicant's provisional application Ser. No.60/403,783 entitled, ‘Implantable Vascular Device,’ filed Aug. 15, 2002which is expressly incorporated by reference herein.

BRIEF DESCRIPTION OF THE DRAWING

Embodiments of the present invention will now be described by way ofexample with reference to the accompanying drawings, in which:

FIG. 1 depicts a cross-sectional view of a native venous valve andretrograde blood flow pattern;

FIG. 2 depicts a schematic view of an illustrative embodiment of thepresent invention in which the prosthesis includes interconnectingproximal and distal sections defining an intermediate, substantiallyopen section for creating an artificial sinus in the vessel;

FIG. 3 depicts a schematic view of a second illustrative embodiment ofthe present invention in which the proximal and distal sections areinterconnected by a frame that is incorporated into the valve structureof the prosthesis;

FIG. 4 depicts a schematic view of an illustrative embodiment of thepresent invention in which the intermediate section of the prosthesiscomprises an expanded portion of the support structure;

FIG. 5 depicts a schematic view of an illustrative embodiment of thepresent invention in which the proximal end is expanded to create anartificial sinus about the valve structure;

FIGS. 6-7 depict side views of embodiments of the present invention inwhich artificial sinus comprises a plurality of separate supportsections;

FIG. 8 depicts a partially sectioned side view of an embodiment of thepresent invention that includes an external sleeve of material;

FIG. 9 depicts a perspective view of a support structure of the presentinvention adapted to increase coaptation of leaflets and pocket sizewithin the vessel;

FIGS. 10-11 depict side views comparing the flow patterns in a standardvalve leaflet configuration with those of the embodiment of FIG. 9; and

FIG. 12 depicts an embodiment of the present invention having acombination of a narrowed intermediate section and the valve structureconfiguration of FIG. 9.

FIG. 13 depicts a side view of an embodiment of the present invention inwhich the leaflets are attached to the parallel struts to increase thearea of coaptation;

FIG. 14 depicts a side view of the embodiment of FIG. 13 that is rotated90.degree. therefrom.

FIG. 15 depicts a top view of the embodiment of FIG. 13.

FIG. 16 depicts an unrolled view of the support frame of the embodimentFIG. 13;

FIGS. 17-18 depict unrolled views of additional embodiments of thepresent invention for increasing the area of leaflet coaptation;

FIGS. 19-20 depict plan views of adaptations in the support structurefor affixing the valve structure thereto; and

FIG. 21 depicts a partially sectioned perspective view of an embodimentin which the support structure does not co-extend along the entirety ofthe leaflet outer edges.

DETAILED DESCRIPTION

The present invention, selected examples of which are illustrated inFIGS. 2-9, 11-20, comprises a collapsible, self expanding or otherwiseexpandable artificial valve prosthesis 10 that is deployed within abodily passageway 20, such as a vessel or duct, of a patient typicallydelivered and implanted using well-known transcatheter techniques forself-expanding prostheses, the valve prosthesis having a first orproximal end 13 and a second or distal end 14, with the normal,antegrade fluid flow typically traveling from the distal end to proximalend of the prosthesis, the latter being located closest to the heart ina venous valve when placed within the lower extremities of a patent. Thevalve prosthesis 10 comprises a support structure 11 and a valvestructure 12, such as the illustrative valve structure, attached aboutthe support structure and configured to selectively restrict fluidflowing therethrough by closing with changes in the fluid pressuredifferential, such as in the presence of retrograde flow. The presentinvention includes structural features that modify the flow dynamicswithin the prosthesis such that fluid collecting in pockets 35 near thebase of the leaflets 26 is more likely to be flushed away or effectivelymixed with fresher incoming bodily fluid on a continual basis.

It should be understood that the materials used to comprise the supportstructure 11 can be selected from a well-known list of suitable metalsand polymeric materials appropriate for the particular application,depending on necessary characteristics that are required(self-expansion, high radial force, collapsibility, etc.). The materialsused for the valve structure 12 can comprise a synthetic material orbiologically-derived material appropriate for the clinical application;however, investigational studies have demonstrated that a bioremodelablematerial (such as an collagenous extracellular matrix (e.g., smallintestinal submucosa), pericardial, or a growth factor-enhanced materialmay have superior anti-thrombogenic properties within the body as thenative cells and tissue gradually replace the original leaflet material.The number of leaflets possible for embodiments of the present inventioncan be two, three, four, or any practical number, but bi-leaflet valvesmay prove advantageous in low-flow venous situation as compared totri-leaflet embodiments, such the type used as heart valves which aresubject to high-flow situations where thrombus formation is far less ofa problem.

In the embodiments of FIGS. 2-8, the support structure 11 is configuredsuch that when the device is deployed within the bodily passage 20, suchas a vein of the lower legs or feet, an artificial sinus 34 is formedadjacent to and surrounding the valve structure 12 such that the bloodor other bodily fluids collecting within the pockets 35 formed aroundthe bases of the valve leaflets 26 is more likely to be flushed out on acontinual basis due to the advantageous geometry created by theartificial sinus 34. The principle is illustrated in the example of FIG.1 which shows a natural venous valve 21 in which retrograde blood 22flowing or falling back down and closing the valve is thought to createa series of vortices 23 as it contacts the leaflets. It is believed thatthe rounded shape of the enlarged natural sinus 37 surrounding the valve21 facilitates creation of these vortices, thereby preventing blood frompooling or stagnating within the pockets 35 at the base of the valve 21,which may lead to thrombus formation or other problems. The presentinvention, by virtue of the configuration of the support structure 11,creates an artificial sinus 34 that attempts to reproduce the functionserved by the natural sinus 37 in the vein.

FIG. 2 depicts a side view of an illustrative embodiment of the presentinvention in which the prosthesis 10 includes a first or proximalsection 15 and a second or distal section 17 that are spaced apart fromone another, defining an intermediate, substantially open section 16 forcreating the artificial sinus 34 in the vessel 20. The term‘substantially open’ is used herein to define a largely unsupportedportion of the bodily passage in which at least some minimalinterconnecting structure (e.g., thin or flexible elements aligned withthe leaflet commissures) is present that traverses the unsupportedportion of the bodily passage, but it comprises very limited surfacearea and typically supplies minimal, if any, force against the walls ofthe passageway lateral to the valve structure 12. The proximal anddistal sections 15,17, which preferably comprise a pair of radiallyexpandable or self-expanding anchoring portions 24, are joined by aninterconnecting means 36, such as the illustrative pair of connectionstruts 18,19 that allows the intermediate section 16 to be otherwiseopen and free of scaffolding so that the vein walls 38 along thatsection of the vessel 20 are able to expand due to pressure exerted bythe blood flowing within the vein.

In the embodiments of the present invention, the anchoring portions 24may function as stents to help the bodily passage remain patent, buttheir primary function is limited to engaging the bodily passage toanchor the prosthesis thereagainst. The support structure 11 andanchoring portions 24 also may be configured to be readily collapsibleas with a normal vein. Since the diameters of the proximal and distalsections 15,17 generally assume a fixed diameter after deployment, theintermediate section, which is mostly unsupported or covered bystructure, expands to form a bulging region of the vessel that functionsas an artificial sinus 34. Although the interconnecting means 36advantageously permit the proximal and distal sections 15,17 to bedeployed together at a fixed distance from one another, it is within thescope of the invention to have the valve prosthesis 10 comprise separateunconnected sections that are deployed sequentially at an effectivedistance from one another to create an artificial sinus 34 therebetween.Additionally, the interconnecting means 36 can comprise suture, fabric,or some other non-rigid material to join the proximal and distalsections 15,17 and define the optimal length of the intermediate section16, without interfering with the creation of the artificial sinus 34. Todeploy a prosthesis 10 having a flexible interconnecting means 36, oneof either the proximal or the distal sections 15,17 can be deployedfirst with the delivery system then being slowly withdrawn until theinterconnecting means 36 becomes taut, whereby the opposite section isthen deployed.

In the illustrative embodiment, the valve structure 12 comprises a pairof leaflets 26 that are situated in the intermediate section andattached to the proximal section 15 at two commissural points 27,28,each located at the proximal ends of the interconnecting struts 18,19,using an appropriate attachment means 30, such as suture, adhesive,fasteners, tissue welding using heat and/or pressure, etc. The leaflets26 are attached about their distal ends 29 to the distal section 17 ofthe support structure 11 using the same or an other suitable attachmentmeans 30. The valve structure 12 is configured so that it advantageouslyexpands with the deployment of the proximal and distal sections 15,17such that the outer edges 39 thereof contact the vessel wallsufficiently to at least substantially prevent leakage of bodily fluidaround the valve structure 12. Optionally, the wall-engaging outer edgesof the leaflets 26 can be reinforced with a separate frame 32 that isattached to or incorporated into the outer edges 37 to improve sealingwith the vessel wall 38. An example of such a frame 32 is depicted inembodiment shown in FIG. 3 in which the frame 32 also serves as theinterconnecting means 36 between the proximal and distal section 15,17of the support structure 11, with the struts 18,19 being laser cut fromthe same tube used to form the remainder of the support structure 11.The valve frame 32 (that portion of the support structure 11 thatreinforces the valve structure 12) can either be configured to exertrelatively little radial force beyond what might be required to ensureadequate contact with the vessel wall 38, or it may be configured suchthat the frame 32 exerts sufficient radial force such that it assists increating an artificial sinus 34 in the portion of the vein along theintermediate section 16 of the valve prosthesis 10.

Another method of creating the artificial sinus 34 is depicted in FIGS.4-5, whereby the support structure 11 includes an expanded portion 31,larger in diameter than the remainder of the support structure 11, thatupon deployment, creates an artificial sinus 34 surrounding the valvestructure 12. The diameter of the artificial sinus 34 caused extendingthe vessel wall 38 is, at its widest point, preferably about 10-120%larger than the diameters of the proximal and distal sections 15,17 whenfully deployed (unrestrained from within the delivery sheath), with amore preferred differential of about 30-80% and a most preferreddifference of 50-70% larger, depending on the diameter of the vein, thevalve structure geometry, fluid column pressures at that location, andother factors. In the illustrative embodiments, the transition betweenthe proximal and distal section 15,17 and the expanded intermediatesection 16 is curvilinear, creating a bulge-like or flared configuration(FIGS. 4 and 5, respectively). In the examples depicted, the supportstructure comprises a single tubular anchoring portion 24 that isplastically, resiliently, or otherwise deformed into a secondconfiguration that includes the expanded portion 31. For example, theanchoring portion 24 can be laser cut from a tube of nitinol, placedaround a mandril having the desired shape, and heat set to produce thefinal desired shape. In the embodiment of FIG. 4, the expanded portion31 comprises the intermediate section 16 of the prosthesis 10, such thatthe artificial sinus 34 is created between the proximal and distalsections 15,17 and the valve structure 12 is located therein. In FIG. 5,the expanded portion 31, which comprises the proximal section 15 of thesupport structure 11, includes a flared configuration that extendsoutward from the distal section 17 (no separately functionalintermediate section 16 is present). The valve structure 12 is attachedabout the proximal end 13, while the flared, expanded portion 31thereabout causes the vessel 20 to bulge outward, thus creating anartificial sinus 34 about the proximal end of the prosthesis 10. Theartificial sinus 34 comprises a combination of a supported and anunsupported portion in the embodiment of FIG. 5. In both illustrativeembodiments the valve structure 12 is sewn to the struts 33 of thesupport structure within the passageway of the anchoring portion 24.Other alternative methods of attachment include adhesives, staples orother fasteners, wire, engagement barbs on the frame, tissue welding,etc.

FIGS. 6-7 depict embodiments similar to that of FIG. 5, except that theproximal, intermediate, and distal sections 15,16,17 comprise separateanchoring portions 24 (having a serpentine or ‘zig-zag’ configuration inthe illustrative embodiment) that are attached to one another inwell-known manner, such as by feeding the illustrative thread material42 or suture through the apices 45 of adjoining bends and securing ittherearound. In the embodiment of FIG. 6, the intermediate section 16comprises a first and a second intermediate subsection 40,41 of opposingfrustoconical-shaped anchoring portion 24 that are coupled to form theartificial sinus 34. The first and second subsections 40,41 can bemanipulated into a frustoconical shape by plastically deforming theanchoring portion 24 into that shape, or by increasing constraint of theframe about the distal end of a cylindrical-shaped proximal portion 15and the proximal end of a cylindrical-shaped distal portion 17 with aconstraining means 42, such as thread, suture, wire, band, covering,etc., so that the respective sections 15,17 assume a frustoconicalshape. Additional constraining means 42 may be included at the first andsecond ends 13,14, as depicted, to maintain the cylindrical shape of theproximal and distal 15,17 sections. The thread or suture 30(constraining means) at the interface 46 interconnecting the first andsecond intermediate subsections 40,41 may or may not function to tensionthe apices 45 of those respective subsections. The illustrativeembodiment of FIG. 7 is similar to that of FIG. 6 except that theintermediate section 16 also comprises a third intermediate subsection43, located between intermediate subsection 40 and 41, that extends thelength of the artificial sinus. The illustrative third intermediatesection 43 comprises a short cylindrical or band-shaped portion whosewidth can be adjusted to create the desired geometry of the artificialsinus 34. Additional subsections can be added as well, if so desired.

FIG. 8 depicts an embodiment in which the support structure 11 comprisesa proximal portion 15 joined to a distal portion 17 by a interconnectingstrut 36, the entire support structure being cut from a single piece ofcannula, such as stainless steel or nitinol. The valve structure 12,comprising a plurality of leaflets 26, is attached to the distal portion17 such that the artificial sinus 34 is formed in the largely open,unsupported region between the proximal and distal sections 15,17 byvirtue of the vessel 20 bulging outward, as in the embodiment of FIG. 2.The valve prosthesis 10 further includes an optional covering 44, suchas an outer sleeve of SIS (or other suitable biological or syntheticmaterial), that is attached to both the proximal and distal sections15,17 of the support structure 11, which helps seal the prosthesis toprevent leakage of retrograde fluid therearound. The covering 44 ispreferably of a constitution and configuration such that it does notinterfere with the creation of the artificial sinus 34.

FIGS. 9,11, and 13-20 comprise embodiments of an artificial valveprosthesis 10 in which support structure 11 carrying the leaflets 26 isconfigured to increase the leaflet contact (coaptable) area 57 about theproximal portion of the valve structure 12 without relying on built-inslack within the material to bring the leaflets in closer proximity andprovide for a extensive sealing area, longitudinally. As defined in thisapplication, the leaflet contact area 57 comprises a longitudinalportion along the valve structure 12 in which the facing surfaces ofopposing leaflets 26 (two or more) coapt or lie in close proximity toone other while in a dry or resting, neutral state (i.e., the pressuredifferentials across the valve orifice are essentially equalized suchthat the leaflets are not being forced together or apart due to externalforces, such as fluid flow), when the prosthesis is an expanded ordeployed configuration. The support frame 11 may be configured formaximizing the extent of the leaflet contact area 57 by including one ormore longitudinal attachment struts 49,50 that define at least theproximal portion 75 of the attachment pathway 74 of each leaflet lateralouter edge 87,88 (the terms outer edge 39 and lateral outer edges 87,88being defined herein as the area or zone along the leaflet thatcomprises the sealing interface). The longitudinal attachment struts49,50/proximal attachment pathways 75 have a substantially longitudinalorientation (e.g., substantially parallel) with respect to thelongitudinal axis 64 of the prosthesis (and valve structure 12). At apoint generally proximate the distal end 89 of the leaflet contact area57 (the proximal portion 96 of the leaflet), the distal portions 76 ofthe adjacent attachment pathways 74 (which are joined proximally about acommissural point) diverge from one another (forming a generallyY-shaped pathway configuration) and assume a much more circumferentialorientation than that of the proximal portion 75 of the pathway suchthat the outer leaflet lateral edges 87,88 of each leaflet converge at apoint lateral to the free inner edge 84 thereof to seal the passagewayand form the distal portion 96 of the leaflet that defines the bottom 96or ‘floor’ of the pocket 55 or intravascular space adjacent the outersurfaces of each of the leaflets, which generally assumes a stronglycupped or curved shape such that the leaflet assumes a generally‘folded’ appearance due to the acutely angled attachment pathway 74 withthe proximal portion of the leaflet having a strong longitudinalorientation with respect to the prosthesis and vessel and the bottomportion 96 having a strongly perpendicular orientation relative to thelongitudinal axis of the vessel and prosthesis. It should be noted thatthe commissures 27,28, while located about the proximal end 13 of theillustrative prosthesis 10, may be located proximal thereto such thatadditional support structure 10 extends proximally, such as in theembodiments of FIGS. 2-8,12.

By extending or maximizing the leaflet contact area and decreasing theradius of the curvature of the leaflet (increasing curvature) about thedistal portion thereof, the basal or distal portion of the pocket 35adjacent each leaflet is enlarged to facilitate and maximize the sizeand/or velocity of the flow vortices 55,56 formed therein duringretrograde flow. During pre-clinical investigations, these broaderpockets have been shown to be especially advantageous in bi-leafletartificial valve designs implanted in the venous system, these valvesexhibiting a marked reduction in thrombus formation as compared toearlier designs. The improvement in flow dynamics for the purpose ofclearing the pocket 35 of stagnant blood that can thrombose andcompromise valve function or lead to other complications is depicted ina comparison of FIGS. 10 and 11. Laboratory analysis of the patterns ofretrograde flow within a valve has shown that multiple vortices aretypically created. In the embodiment of FIG. 10, which has a generally(inverted) V-shaped attachment pathway 74, a first vortex 55 is createdbelow which a second, smaller vortex 56 is usually present, usuallyhaving opposite flow, which may be at least partially inadequate forclearing away blood pooling about the base of the leaflets 60,61 in avenous valve. In the embodiment of the present invention depicted inFIG. 11, which has a generally (inverted) Y-shaped attachment pathway74, the larger pocket (at least at the basal portion) allows for alarger and stronger second vortex 56 of fluid created by retrograde flowthat is more optimal for clearing away any pooling blood that wouldotherwise collect there and potentially provide for greater downforce onthe leaflets 60,61 to improve closure of the valve.

FIGS. 9 and 11 depict an artificial venous valve prosthesis 10 in whichthe frame 32 of the support structure 11 is configured such that thepair of longitudinal attachment struts 49,50 extending from each of thecommissures 27,28 that represent the proximal attachment points for thevalve structure (not shown) form a first angle 47 (.alpha.) with respectto one another that is less than the second angle 48 (.beta.) that isformed between the distal attachment struts 51,52, which comprisecontinuations of the longitudinal attachment struts 49,50 (togethercomprising the legs 58 of the frame 32), and the inside 63 of the vesselwall 38. The first angle 47 is preferably between −10 and 30.degree. (anegative angle being possible with a sufficiently large-radius bendabout the commissure) with a more preferred angle being 0-25.degree. anda most preferred angle of 0-10.degree. The longitudinal attachmentstruts 49,50 may both diverge and converge at various points therealong(i.e., bow inward or outward), which in case, the first angle may berelevant for only the proximal portion 75 or is measurable betweenvectors representing the best straight line longitudinally traversingeach strut 49,50. The illustrative embodiment also includes a pair ofoptional stabilizing arms 53,54 that extend laterally from the legs58,59 to help center the prosthesis 10 within the vessel 20. Ideally,the angles depicted in the frame 32 configuration of FIG. 11 results inthe opposing leaflets 60,61 being much more in alignment (e.g.,parallel) with one another than in a prosthesis where the angles 47,48are relatively the same, such as the prior art valve shown in FIG. 10,particularly over the proximal half of the leaflets 60,61. The result isthe creation of a larger pocket around the base of the leaflets 60,61that helps create larger and/or stronger vortices of retrograde bloodflow. A second clinical benefit is that there is a larger area ofcoaptation between the leaflets 60,61, which helps provide a better sealagainst possible reflux through the valve orifice.

FIGS. 13-18 depict another group of embodiments configured formaximizing the coaptation distance or region between the leaflets inwhich the attachment pathway 74 comprises a proximal portion 75 thatgenerally extends along one or more longitudinal attachment struts 49,50that are generally aligned with the longitudinal axis 64 of theprosthesis and a distal portion 76 that is angled laterally from thelongitudinal attachment struts and generally follows the distalattachment struts 51,52 which unlike the embodiment of FIG. 9, extendlaterally outward from the longitudinal struts 49,50 as separate struts.As with the embodiment of FIG. 9, the distal attachment struts/portionsconverge at a point oppositely facing each leaflet 60,61 where theyattach to the lateral support structure 53,54, which helps center theprosthesis in the vessel and protects the leaflets from adhering to thevessel wall. In the embodiments of FIGS. 13-17, the support frame 11further includes proximal support arms 77,78 that attach to and extendfrom the longitudinal attachment struts 49,50 about the commissurepoints 27,28 and provide an interconnection with the lateral supportstructure 53,54 (also shown in FIG. 15).

The embodiment depicted in FIGS. 13-14 comprises a pair of longitudinalattachment struts 49,50, generally parallel to one another, which areadapted for attaching the respective leaflets 26 therealong, thuscreating a large leaflet contact or coaptable area 57 that extends overhalf of the length of the prosthesis. As depicted in FIG. 16, Thelateral support structure 53,54 shares or mirrors the configuration ofthe longitudinal attachment strut regions which they interconnect,except that they are located 90.degree. therefrom and orientedoppositely thereto, such that the support structure 11 generally forms aserpentine configuration adapted to be readily collapsible andexpandable. In the illustrative embodiment, the support structure 11 orframe can be divided into four sections or quadrants 70,71,72,73 thatare identical except for their orientation, sections 70 and 72 beingoriented with the commissures 27,28 and longitudinal attachment struts49,50 carrying the valve structure 12 being oriented proximally towardthe first end 13 of the prosthesis 10. The repeating, uniform design ofthe support structure 11 of the illustrative embodiment advantageouslyprovides better structural stability, compressibility/expandability, andoverall integrity than a support structure that does that comprise anon-uniform, non-repeating frame pattern.

The lateral arms 77,78 of the lateral support structure 53,54, thatconnect to the longitudinal attachment struts 49,50 each include a strut68 that carries a proximal radiopaque marker 67 used to facilitateorientation of the device 10 and provide additional support. Anidentical distal strut 90 and an optional radiopaque marker 91 islocated distal to the longitudinal attachment struts 49,50 and attachedto the distal attachment struts 51,52 to serve a similar orientation andstabilization function. An integral barb 25 is located about thecommissural bends 27,28 that interconnect the longitudinal attachmentstruts 49,50. The parallel longitudinal attachment struts 49,50 are alsointerconnected about their distal ends by a short interconnecting strut81 such that an elongate closed cell 92 is formed. The width of cell 92is not critical, although it may be made sufficiently narrow such thatit serves to further pin or anchor the leaflets 60,61 to the struts49,50, which could be especially advantageous in fixation if the leafletmaterial retracts during the remodeling process. A preferred widthbetween the two struts 49,50 would be between 0-5 mm, with 0-3 mm beingmore preferred and 0-1 mm being most preferred. If the spacing is toowide, gaps may be created between the opposing leaflets which couldallow for an unacceptable amount of reflux through the valve.

A similar frame design is shown in FIG. 17 which includes a singlelongitudinal attachment strut 49 to which both leaflets 60,61 are sewnor otherwise attached allowing for similar extended coaptation betweenleaflets. The leaflets 60,61 can be attached such that each abuts thestrut 49 (and sewn or attached without being wrapped over the strut) orthe first lateral leaflet edge (not shown) is wrapped around the strut49 while the second leaflet lateral edge of the opposite leaflet is sewnover the first lateral leaflet edge and strut 49. The single attachmentstrut can be of a width that is generally uniform with respect to theother support structure or it may be made substantially thicker, such asshown in FIG. 19. Furthermore, a thicker strut 49 could includeapertures 93 or slots of any shape or length distributed therealong forreceiving sutures or other attachment elements 30, such as clips, rings,etc., for affixing or anchoring the leaf outer edges thereto. FIG. 20depicts an embodiment having a pair of longitudinal attachment struts49,50 with anchoring structure 95, such as the illustrative scallopededge that is strategically configured therealong to help prevent orlimit the attachment element 97 and the valve structure itself, fromsliding down the longitudinal attachment struts 49,50, especially duringany retraction that may occur with a bioremodelable material. Theanchoring structure can comprise any projections or other structure thatprovides a shoulder or irregularities along the edges of the struts thathelps limit sliding of the leaflets along the longitudinal attachmentstruts 49,50. Further examples of adaptations for limiting movement ormigration of attachment elements (e.g., sutures) and covering materialare disclosed in an application to Case et al. (U.S. Ser. No.10/820,918), entitled ‘Intraluminal Support Device with Graft’ and filedApr. 8, 2004, which is expressly incorporated by reference herein.

FIG. 18 depicts an embodiment having generally, but not absolutelyparallel longitudinal attachment struts 49,50 which slightly convergetoward the distal end 14 of the prosthesis 10 (and are spaced moredistant from each other than the embodiment of FIGS. 13-14. Thecommissural bends 27,28 and distal bends 82 interconnect thelongitudinal attachment struts and form a closed cell 92 as in theembodiment of FIGS. 13-16. The distal attachment struts 51,52 providethe interconnection between the opposite closed cells 92 as well as thedistal portion 76 of the attachment pathway 74. They also carry alateral arm 93 and together comprise the lateral support structure 83,84that provide longitudinal support/stabilization and leaflet protection.The embodiment of FIG. 18 lacks proximal support arms 77,78 of theembodiment of FIGS. 13-16.

The illustrative support structure 11 in FIGS. 9, 11, 13-18 is notcritical to achieve the optimal leaflet angles in the valve structure 12for creating larger pockets, as depicted. For example, the attachmentpathway 74 of the valve structure 12 can comprise an attachment to anoutside support frame to form the illustrative configuration with theframe 32 that is not necessarily extending along the outer edges 39 ofthe leaflets 60,61, but rather attached to selected strut that cross theattachment pathway 74, especially along the distal portion 76 of thepathway. Furthermore, at least a portion of the outer edges 39 can bedirectly affixed to the vessel wall (such as being sutured, heat welded,or anchored with barbs, adhesives, etc.) with the frame 11 being absentor reinforcing or shaping only a limited portion of the leaflet outeredges 39, thus allowing for the vein to naturally collapse (at leastpartially) when not filled with blood. In the example depicted in FIG.21, the frame 11 comprises a partial support 98 of a hair-pinconfiguration that includes a proximal bend about each commissure 27,28with free-ended longitudinal attachment struts 49,50 extending therefromwhich help form the leaflet angle 47, while the distal portion 76 of theattachment pathway 74 comprises an alternative attachment that does notresult in the leaflet material being urged thereagainst by a radiallyexpandable frame. Methods include surgical attachment, tissue welding,adhesives, barbs and other well-known methods, teachings of which isincluded in a co-pending U.S. patent application entitled,‘Percutaneously Deployed Vascular Valves with Wall-Adherent Adaptations(Case et al.) filed Apr. 1, 2004 (Ser. No. to be added by amendment),the disclosure of which is expressly incorporated by reference herein.The angle of the leaflets 60,61 relative to the longitudinal axis 64 ofthe prosthesis and vessel (half of the first angle 47 or .alpha./2) ispreferably −5-15.degree. with a more preferred angle of 0-10.degree. anda most preferred angle of 0-5.degree. The relatively small or shallowangles of the longitudinal attachment struts 49,50 about the commissures27,28 allows for a larger space adjacent the leaflets 60,61 and broaderpockets 35 at the base of the leaflets. The longitudinal attachmentstruts 49,50 of the support structure can be formed generally parallelto one another along the proximal portions of the longitudinalattachment struts 49,50 to create the maximum pocket size and greatercoaptation of the leaflets. For example, the pocket 35 areas would bemaximized in an attachment pathway 74 where angle 47 is zero (or anegative angle) and angle 48 is at least 90.degree., such that theattachment pathway along each leaflet lateral outer edge 87,88 isgenerally L-shaped such that the distal portion 76 of the attachmentpathway angles abruptly from the proximal portion rather than assuming adog-leg configuration as shown in the illustrative embodiments.

The amount of contactable or coaptable area 57 can be expressed indifferent ways. In the present invention, the length of the leafletcontact area 57 (or proximal portion 75 of the attachment pathway) in atypical venous valve prosthesis is preferably at least 2 mm and as muchas 50 mm (depending on the configuration of the valve prosthesis), witha more preferred length of 5-30 mm and a most preferred range of 5-15mm. In an average sized venous valve having a length of 25 mm, thepreferred range of the leaflet contact area 57 or proximal attachmentpathway 75 would be 10-80% of the prosthesis length (2.5-20 mm),assuming the valve structure 12 is generally as long as the supportframe 11. A more preferred leaflet contact area 57 would comprise 30-60%with 35-55% being most preferred in a prosthesis of the same generaltype as depicted. The relationship between leaf contact area and thediameter of the vessel may be a factor in optimizing the functionalityof the valve prosthesis 10. Preferably, the length of the longitudinalattachment struts 49,50 and/or leaflet contact area 57 is 25 to 250% ofthe nominal vessel diameter with a more preferred range of 25-150%.

The amount of slack in the leaflet material also helps determine howwell the leaflets coapt during retrograde flow and how large of anopening they permit during antegrade flow. Preferably, but notessentially, the prosthesis is configured such that the distance formedbetween the leaflets in their fully open position and the vesseldiameter remains preferably between 0-100% of the vessel diameter, witha more preferred range of 20-80% of the vessel diameter and a mostpreferred range of 50-70%. By substantially orienting the longitudinalattachment struts 49,50 with the longitudinal axis 64 of the prosthesis,less slack is necessary for optimal or extended coaptation. Not havingthe leaflets regularly contact the outer walls of the vessel can beespecially important when using a bioremodelable material, such as anECM, which can partially or completely adhere to the wall over time astissue grows into the leaflets, thus compromising the functionality ofthe valve.

FIG. 12 depicts an embodiment having different structural configurationto after retrograde fluid flow patterns within the pocket to preventpooling of blood or bodily fluid. The support structure 11 includesproximal and distal sections 15,17 which are sized and configured toexpand and engage the walls 38 when the valve prosthesis 10 is deployedwithin the bodily passage 20. The intermediate section 16, whichincludes the valve structure 12, is narrower than each of the adjoiningproximal and distal sections 15,17. A covering of biologically-derivedor synthetic biocompatible or bioremodelable material 44, such as acollagenous extracellular matrix (ECM) (e.g., SIS), pericardial tissue,or fabric, such as DACRON, ePTFE, etc., is attached over or inside thesupport structure to enclose passageway 62 and to help seal theprosthesis with the vessel. The proximal and distal sections 15,17 aregenerally frustoconical or bowl-shaped with the interface 46 with theproximal or distal end of the intermediate section 16 being smaller indiameter than the proximal or distal ends 13,14 of the prosthesis. Bynarrowing the passageway 62 of the prosthesis 10 at the point where ittransitions between the proximal section 15 and the intermediate section17, a Venturi effect is created in which the retrograde flow isaccelerate, which advantageously produces enhanced flushing action(e.g., stronger vortices) within the pockets 35 surrounding the leaflets60,61. The ability of the valve prosthesis 10 to prevent pooling ofblood or fluid around the pockets 35 is further enhanced in theillustrative embodiment by configuring the leaflets 61,62 as in theexample shown in FIG. 11. It is not necessary to the invention that theproximal and distal sections share the same configuration. Therespective sections 15,16,17 may be separate, attached units, as shown,or represent subsections of a single anchoring portion 24, similar tothe embodiment of FIG. 4.

It should be noted that the support structure and valve structure shownin each of the figures in the application are merely exemplary of thenumerous well-known possibilities, many others of which are disclosed inU.S. patent application Ser. No. 10/642,372 entitled, ‘ImplantableVascular Device,’ filed Aug. 15, 2003 and whose disclosure is expresslyincorporated by reference herein. For example, the valve structure maycomprise more than the illustrative two leaflets or comprise leaflets ofother shapes and configuration. The valve structure may also comprise anon-leaflet valve such as one or more tubular sleeves or otherconfigurations adapted to restrict fluid flow. With regard to thesupport structure, it may be formed from wire, cut from a section ofcannula, molded or fabricated from a polymer, biomaterial, or compositematerial, or a combination thereof. The pattern (i.e., configuration ofstruts and cells) of the anchoring portion(s) that is selected toprovide radial expandability to the prosthesis is also not critical foran understanding of the invention. Any other undisclosed or incidentaldetails of the construction or composition of the various elements ofthe disclosed embodiment of the present invention are not believed to becritical to the achievement of the advantages of the present invention,so long as the elements possess the attributes needed for them toperform as disclosed. The selection of these and other details ofconstruction are believed to be well within the ability of one of evenrudimentary skills in this area, in view of the present disclosure.Illustrative embodiments of the present invention have been described inconsiderable detail for the purpose of disclosing a practical, operativestructure whereby the invention may be practiced advantageously. Thedesigns described herein are intended to be exemplary only. The novelcharacteristics of the invention may be incorporated in other structuralforms without departing from the spirit and scope of the invention. Theinvention encompasses embodiments both comprising and consisting of theelements described with reference to the illustrative embodiments.Unless otherwise indicated, all ordinary words and terms used hereinshall take their customary meaning as defined in The New Shorter OxfordEnglish Dictionary, 1993 edition. All technical terms shall take ontheir customary meaning as established by the appropriate technicaldiscipline utilized by those normally skilled in that particular artarea. All medical terms shall take their meaning as defined by Stedman'sMedical Dictionary, 27^(th) edition.

1-29. (canceled)
 30. A radially expandable artificial valve prosthesisfor implantation in a vessel having a vessel wall, comprising: a supportstructure, comprising: a proximal section comprising a first radiallyexpandable anchoring portion having a plurality of struts interconnectedby bends; a distal section comprising a second radially expandableanchoring portion having a plurality of struts interconnected by bends;the proximal and distal sections spaced apart from one another to definean intermediate section disposed between the proximal and distalsections, the intermediate section comprising a substantially opensection of the support structure; a first connection strut connectedwith the proximal and distal sections and spanning the intermediatesection; and a second connection strut connected with the proximal anddistal sections and spanning the intermediate section; and a valvestructure attached to the support structure and configured toselectively restrict fluid flow through the support structure by closingwith changes in the fluid pressure differential across said valveprosthesis.
 31. The radially expandable valve prosthesis of claim 30,wherein the valve structure is situated in the intermediate section ofthe support structure.
 32. The radially expandable valve prosthesis ofclaim 31, wherein the intermediate section has a first length theextends along a lengthwise axis of said valve prosthesis; wherein thevalve structure has a second length that extends along the lengthwiseaxis of said valve prosthesis; and wherein the first length is greaterthan the second length.
 33. The radially expandable artificial valveprosthesis of claim 30, wherein the proximal section defines a firstcircumference and the first connection strut is connected with a firstattachment point on the first circumference; and wherein the distalsection defines a second circumference and the first connection strut isconnected with a second attachment point on the second circumference;and wherein the first and second attachment points lie on a firstlongitudinal axis of said artificial valve prosthesis.
 34. The radiallyexpandable artificial valve prosthesis of claim 33, wherein the secondconnection strut is connected with a third attachment point on the firstcircumference; and wherein the second connection strut is connected witha fourth attachment point on the second circumference; and wherein thethird and fourth attachment points lie on a second longitudinal axis ofsaid artificial valve prosthesis that is different than the firstlongitudinal axis.
 35. The radially expandable artificial valveprosthesis of claim 34, wherein the first and second longitudinal axesare disposed substantially opposite each other with respect to acentrally-disposed longitudinal axis of said valve prosthesis.
 36. Theradially expandable artificial valve prosthesis of claim 30, wherein theproximal section defines a first circumference and the first connectionstrut is connected with a first attachment point on the firstcircumference; and wherein the distal section defines a secondcircumference and the first connection strut is connected with a secondattachment point on the second circumference; and wherein the firstattachment point lies on a first longitudinal axis of said artificialvalve prosthesis and the second attachment point lies on a second,different longitudinal axis of said valve prosthesis.
 37. The radiallyexpandable valve prosthesis of claim 36, wherein the first and secondattachment points are approximately 90° out of phase with each otherrelative to a centrally-disposed longitudinal axis of said valveprosthesis.
 38. The radially expandable valve prosthesis of claim 36,wherein the second connection strut is connected with the firstattachment point on the first circumference and a third attachment pointon the second circumference; wherein the third attachment point lies ona third, different longitudinal axis of said artificial valveprosthesis.
 39. The radially expandable valve prosthesis of claim 30,wherein the first and second connection struts comprise linear strutsdisposed substantially opposite each other with respect to acentrally-disposed longitudinal axis of said valve prosthesis.
 40. Theradially expandable valve prosthesis of claim 30, wherein theintermediate section includes interconnecting structure consisting ofthe first and second connection struts.
 41. The radially expandablevalve prosthesis of claim 30, wherein the valve structure is attached tothe first and second connection struts.
 42. The radially expandablevalve prosthesis of claim 30, wherein the valve structure comprises asingle leaflet.
 43. The radially expandable valve prosthesis of claim30, wherein the valve structure comprises two leaflets.
 44. The radiallyexpandable valve prosthesis of claim 30, wherein the valve structurecomprises a synthetic material.
 45. The radially expandable valveprosthesis of claim 44, wherein the valve structure comprises DACRON.46. The radially expandable valve prosthesis of claim 44, wherein thevalve structure comprises ePTFE.
 47. The radially expandable valveprosthesis of claim 30, wherein the valve structure comprises abiologically-derived material.
 48. The radially expandable valveprosthesis of claim 47, wherein the valve structure comprises abioremodellable material.
 49. The radially expandable valve prosthesisof claim 48, wherein the valve structure comprises an extracellularmatrix material.
 50. The radially expandable valve prosthesis of claim49, wherein the valve structure comprises small intestine submucosa. 51.The radially expandable valve prosthesis of claim 30, wherein thesupport structure comprises a metal.
 52. The radially expandable valveprosthesis of claim 51, wherein the support structure comprisesstainless steel.
 53. The radially expandable valve prosthesis of claim51, wherein the support structure comprises a superelastic material. 54.The radially expandable valve prosthesis of claim 53, wherein thesuperelastic material comprises nitinol.
 55. The radially expandablevalve prosthesis of claim 30, wherein the support structure comprises apolymeric material.
 56. A radially expandable artificial valveprosthesis for implantation in a vessel having a vessel wall,comprising: a support structure, comprising: a proximal sectioncomprising a first radially expandable anchoring portion having aplurality of struts interconnected by bends and defining a firstcircumference; a distal section comprising a second radially expandableanchoring portion having a plurality of struts interconnected by bendsand defining a second circumference; the proximal and distal sectionsspaced apart from one another to define an intermediate section disposedbetween the proximal and distal sections, the intermediate sectioncomprising a substantially open section of the support structure; andfirst and second connection struts spanning the intermediate section andconnected with the proximal and distal sections, each of the first andsecond connection struts connected with a first attachment point on thefirst circumference; and a valve structure attached to the supportstructure and configured to selectively restrict fluid flow through thesupport structure by closing with changes in the fluid pressuredifferential across said valve prosthesis.
 57. A radially expandableartificial valve prosthesis for implantation in a vessel having a vesselwall, comprising: a support structure, comprising: a proximal sectioncomprising a first radially expandable anchoring portion having aplurality of struts interconnected by bends and defining a firstcircumference; a distal section comprising a second radially expandableanchoring portion having a plurality of struts interconnected by bendsand defining a second circumference; the proximal and distal sectionsspaced apart from one another to define an intermediate section disposedbetween the proximal and distal sections, the intermediate sectioncomprising a substantially open section of the support structure; andfirst and second curvilinear connection struts spanning the intermediatesection and connected with the proximal and distal sections, each of thefirst and second curvilinear connection struts connected with a firstattachment point on the first circumference and a second attachmentpoint on the second circumference; and a valve structure attached to thesupport structure and configured to selectively restrict fluid flowthrough the support structure by closing with changes in the fluidpressure differential across said valve prosthesis.